A teasingly tricky maths challenge that claims to separate the real boffins from those who just claim to know the answers is sweeping Facebook.Some three million people have already taken the tricky ‘Intelligence Test’ which carries a ‘share if you understand’ tag on it.Unsurprisingly, a shed-load of people have shared it, keen to show that they have an IQ of more than 150, apparently what you need to be able to understand it.

However, one doubting brainbox has devised a ‘test for a test’ to see if those who are sharing the solution to the problem really do know their stuff.YouTuber Presh Talwalker created something which needs the same logic from the test to be applied to another piece of maths to get a correct answer.Talwalker says of the new test: ‘If you understand the rule you should be able to solve this problem.’ THE QUESTION: Based on the intelligence test rule: x + y = (x – y) (x + y) and using the pattern below to help you, work out how ?+? = 1236 + 4 = 2109 + 2 = 7118 + 5 = 3135 + 2 = 377 + 6 = 113 9 + 8 = 11710 + 6 = 41615 + 3 = 1218

THE SOLUTION If you split the answer of 123 in two: you get two numbers 1 and 23To work back to what the numbers in question are, you need to work out two numbers where the second subtracted from the first makes 1 and also both added together makes 23.YouTuber Talwalker has written a formula for the ?+? part, calling the first number in question x and the second number y.Using these and the numbers 1 and 23 split out of the answer delivers:x – y = 1x + y = 23This corresponds to:12 – 11 = 112 + 11 = 23Write you them together and you get 123, as in the brainteaser question which is written 12 + 11 = 123Are you still with us? Then congratulations, you’re a genuine boffin…

n the Youtuber’s slide above, the top line shows how the brainteaser question is written…but be careful, don’t mistake this for an actual equation where you do the sum.
Below this a formula showing some of the working on how to get back from 123 to what the two question mark numbers are.
The formula calls the first number in question x and the second y.
If you know how the brainteaser question works, you will know that you need to work out two numbers where the second subtracted from the first makes the first number in the answer (in this case 1) and both added together makes the second number in the answer (in this case 23).
So, in this instance:
x – y = 1
x + y = 23
We can add these two together, which would be written out like this (x-y)+(x+y)=24
In this equation we have 2x (a positive x plus a positive x) and no y (a negative y plus a positive y), so:
2x=24
That means that x is 12, so using the first formula:
12-y=1
That means that y is 11.
Write these numbers in the style of the brainteaser and you get 12+11=123